Perhaps all you're really looking for is a growth inhibitor. Chelators have
such activity against some microbes (particularly those that require Fe). I
assume from condition #4, he is constantly monitoring the aggregation
process by UV(?) If not, then short wave UV is also microcidal. Can he
tolerate a range of pH? A pH value at the extreme of his tolerance might
also give him sufficient growth inhibition. Just some thoughts off the top
of my head. Good luck.
jw